Photocatalysis　has　attracted　much　attention　as　an　emerging　algae　removal　technology,　but　the　inactivation　performance　is　inevitably　affected　by　the　extracellular　polymeric　substance　(EPS)　produced　by　algae.　In　this　study,　a　photocatalyst　(Ag2O/g-C3N4)　with　efficient　algae　inactivation　is　adopted　to　investigate　the　interactions　with　EPS,　and　the　impact　of　EPS　on　photocatalytic　algae　removal　is　studied.　The　results　show　that　EPS　can　adhere　to　the　surface　of　Ag2O/g-C3N4　by　electrostatic　force.　The　interaction　with　EPS　decreases　the　surface　zeta　potential　of　the　Ag2O/g-C3N4　from　7.71　to　−22.3 mV　with　the　increase　in　EPS　concentration,　and　the　maximum　ratio　of　particle　size　increases　from　825　to　1281 nm.　In　addition,　the　interaction　with　EPS　inhibits　the　release　of　Ag+　in　Ag2O/g-C3N4　by　half,　thus,　the　toxicity　of　metal　ions　will　be　alleviated.　Meanwhile,　EPS　can　also　be　degraded　by　Ag2O/g-C3N4,　indicating　that　EPS　can　work　as　a　radical　scavenger　to　protect　the　algae　cells.　Without　the　protection　of　EPS,　97.8%　of　algae　cells　are　inactivated　after　5　h　photocatalysis.　Therefore,　more　attention　should　be　given　to　the　interaction　between　EPS　and　photocatalyst　to　promote　the　design　and　application　of　the　photocatalytic.　©　2020　Wiley-VCH　GmbH